Data storage systems

ABSTRACT

A DATA STORAGE MEDIUM COMPRISING A SUPPORT AND A RADIATION SENSITIVE TITANIUM DIOXIDE, THE TITANIUM DIOXIDE HAVING BEEN HEATED AT AN ELEVATED TEMPERATURE AND FOR A TIME PERIOD SUFFICIENT TO INCREASE THE PHOTOGRAPHIC SPEED THEREOF. PREFERABLY, THE TITANIUM DIOXIDE HAS BEEN HEATED TO A TEMPERATURE OF AT LEAST 200*C. FOR A TIME PERIOD OF AT LEAST 0.5 HOUR. THIS COPY MEDIUM CAN THEN BE EXPOSED TO ESTABLISH AN IMAGE PATTERN AND IF DESIRED, CONTACT WITH SUITABLE IMAGE FORMING MATERIAL TO ESTABLISH A PERMANENT IMAGE. PREFERRED IMAGE FORMING MATERIALS COMPRISE A LIQUID REDOX SYSTEM SUCH AS SOLUTION OF METAL IONS.

United States Patent 6 U.S. C]. 96-27 Claims ABSTRACT OF THE DISCLOSURE A data storage medium comprising a support and a radiation sensitive titanium dioxide, the titanium dioxide having been heated at an elevated temperature and for a time period sutiicient to increase the photographic speed thereof. Preferably, the titanium dioxide has been heated to a temperature of at least 200 C. for a time period of at least 0.5 hour. This copy medium can then be exposed to establish an image pattern and if desired, contacted with suitable image forming material to establish a permanent image.

Preferred image forming materials comprise a liquid redox system such as a solution of metal ions.

This application is a continuation of application Ser. No. 463,037, filed June 10, 1965, and now abandoned.

Data or image storage media comprising radiation sensitive titanium dioxide are described in detail in U.S. Pats. 3,152,903; 3,152,904; 3,052,541; French Pats. 345,- 206 and 1,245,215, and in commonly owned copending U.S. patent application Ser. No. 199,211, filed May 14, 1962, by Elliot Berman et al. and now abandoned. In the aforesaid U.S. patent application, radiation sensitive titanium dioxide functions as the photosensitive component of the media. As described in said application, exposure of said media to a pattern of radiant energy results in the storage of a reversible image pattern of radiant energy results in the storage of a reversible image pattern therein. The reversible image pattern exists for a limited time during which said pattern can be converted to an irreversible form and read out visually by contacting said pattern with chemical redox systems. In the aforesaid U.S. and French patents, the radiation sensitive titanium dioxide apparently functions as an accelerator or as an auxiliary photosensitive component of the media described. In view of the many image storage systems having media comprising radiation sensitive titanium dioxide, improved media of this type which are especially advantageous in said systems would be indeed a not-able contribution to the art.

A principal object of the present invention is to provide improved data storage systems.

Another object of the present invention is to provide improved data or image storage systems involving media comprising titanium dioxide as a component thereof.

Another, more specific object of the present invention is to provide an improved image storage system wherein said image is stored in reversible form in media comprising radiation sensitive titanium dioxide.

Still another object of the present invention is to provide an improved storage system wherein the image pattern obtained upon exposure of the media can be converted to an irreversible form at a preselected time or space remote from that at which said exposure occurred.

Still another specific object of the present invention is to provide an image storage system wherein the image pattern obtained upon exposure of the media can be selectively erased from said media or altered while stored in said media, such as by addition thereto.

Another object of the present invention is to provide a method for selectively adjusting the principal photographic properties of image storage media comprising radiation sensitive metal oxides and for producing image storage media of predetermined photographic properties.

Still other objects and advantages of the present invention will in part be obvious to those skilled in the art or will in part appear hereinafter.

Broadly, the abovementioned objects and advantages are realized in accordance with the practice of the present invention by including in data or image storage media of the type described, a particular titanium dioxide which has been aftertreated at elevated temperatures in an oxidizing atmosphere. More precisely, I have found that surprisingly improved photographic properties of such data storage media can be obtained by including therein a heat treated, radiation sensitive titanium dioxide which had an initial particle size substantially less than about 1 micron and a nitrogen surface area of less than about 60 square meters per gram prior to the heat treatment thereof.

The best balance of improved properties are obtained in media comprising a heat treated titanium dioxide which was produced by the high temperature pyrolysis of titanium halides and, as produced, had an initial average particle diameter of less than about 0.2 micron and an initial nitrogen surface area of less than about 60 square meters per gram. Accordingly, media comprising a heat treated titanium dioxide of the abovementioned initial properties constitute the most preferred embodiment of my invention. It is to be understood that, by average particle diameter, I mean a mixture of particles in which the normal number average distribution of particle diameters has a maximum at no greater than about the particle diameter recited, although decreasingly smaller numbers of larger particles or of smaller particles may be present.

In accordance with the practice of my invention, titanium dioxides of the abovementioned initial properties are heated in an oxidizing atmosphere, such as air, oxygen, or ozone enriched air, at temperatures between about 200 C. to about 950 C. for from about 0.5 hour to about 30 hours (or longer, if desired). The most especially preferred temperatures and times of heating are between about 400 C. to about 650 C. and from about 2 hours to about 5 hours, respectively.

Many manners of treating the titanium dioxides at elevated temperatures are included Within the scope of my invention. For example, the heat treatment can be conveniently accomplished in either a bulk or continuous fashion. An especially perferred method involves establishing a shallow bed of titanium dioxide on an endless belt which is conducted through a furnace maintained at elevated temperatures.

After heat treatment, the titanium dioxide can be advantageously included in any of the media described in the aforementioned patents and application. It is to be understood that the heat treated titanium dioxide can be applied to any of the diverse substrates mentioned in the aforesaid patents and application and in the manners described there. The substrate can be flexible or rigid and can be of such materials as glass, wood, cloth, plastic, paper, metal, and the like. Also, the improved media of the present invention can comprise many optional ingredients such as the binders, dye sensitizers, dopants, and the like which are useful in image storage media of the type described in said patents and application. I

An especially preferred embodiment of the present invention relates to media comprising radiation sensitive titanium dioxide which are transmissive of visible light, i.e., suitable for projection viewing. Accordingly, transparent or translucent binders and substrates are especially advantageous when combined with the heat treated titanium dioxide of the present invention. Representative preferred binders are those organic resins which are either transparent or translucent when cured, such as a copolymer of styrene and butadiene, more commonly known as Pliolite, and polyamide, more commonly known as Zytel 61. Representative preferred transparent or translucent substrates include those comprising polyethylene terephthalate, polyesters, cellulose acetate, and the like.

Details of my invention and of the benefits to be obtained therefrom will be better understood by reference to the following examples which describe methods of practicing same. The following examples are to be considered as illustrative in nature and in no way are they to be construed so as to limit my invention beyond those limitations expressly set forth in the present specification or in the claims which appear hereinafter.

EXAMPLE 1 Sixteen parts by weight of a finely divided titanium dioxide--Cabot P-25having an average particle size of about 0.03 micron and an initial surface area of about 40 square meters per gram were dispersed in about 75 parts by weight of water in which 0.32 part by weight of sodium hexametaphosphate had been added as a dispersing agent. The pigment was added with stirring, and the mixture was thoroughly agitated to disperse the titanium dioxide un1 formly therethrough.

About 8.5 parts by weight of 47 percent Rhoplex, aqueous polyacrylate latex, were next combined with the dispersion containing the particulate titanium dioxide. he mixture, which was thoroughly stirred, thus contained about 4 parts of acrylate solids by dry weight, so that the weight ratio of TiO to binder solids was 4 to 1. The resulting mixture was coated on a transparent substrate. The coating weight of said photosensitive medium was about six pounds per 3,000 square feet.

The medium was then exposed to a standard xenon flash source in a Mark. VI EG&G sensitometer for about seconds.

The medium so exposed was then immersed in a saturated methanolic solution of silver nitrate and subsequently in an amplification solution comprising about 30 grams of phenidone and 30 grams of citric acid in about one liter of methanol.

The photographic properties of the above medium were determined in accordance with a standard sensitometry technique as described in detail in a publication entitled Sensitometry and Grading of Photographic Papers published by the American Standards Association in 1953. The following data were obtained:

TABLE l.-PHO'I=OGRAPHIC PROPERTIES Gamma (contrast) 1.1 Speed 14 Maximum optical density 1.1 Fog level 0.0

EXAMPLE 2 A sample of the Cabot P-25 of Example 1 was heated in air at a temperature of 650 C. for about 2 hours.

After heat treatment, the nitrogen surface area was 65 square meters per gram while the average particle diameter appeared to be relatively unaffected.

Thereafter the titanium dioxide so heat treated was included in an image storage medium and an image stored in and retrieved therefrom in accordance with the pocedure set forth in Example 1.

The photographic properties of the medium were determined as in Example 1 and the following data were obtained:

TABLE 2.-PHOTOGRAPHIC PROPERTIES Gamma (contrast) 0.98 Speed -s 165 Maximum optical density 1.1 Fog level nnnnnnnnnnnnnnnnnnnn H 0.09

4 EXAMPLE 3 Substantially the same procedure as set forth in Example 1 was followed, but, instead of Cabot P-25, a precipitated titanium dioxide was included as the photosensitive component of the medium. The precipitated titanium dioxide had an initial average particle size of about 0.2 micron and an initial nitrogen surface area of about 10 square meters per gram.

.The photographic properties of the medium were determined and the following data were obtained:

TABLE 3.-PHOTOGRAPHIC PROPERTIES Gamma (contrast) 0.76

Speed 7.0

Maximum optical density 0.80

Fog level 0.08

EXAMPLE 4 Substantially the same procedure as set forth in Example 2 was followed, but, instead of Cabot P-25, the precipitated titanium dioxide of Example 3 was heated in air at a temperature of 400 C. for about 3 hours.

The photographic properties of the image storage medium comprising the precipitated titanium dioxide so heat treated were determined and the following data were obtained:

TABLE 4.PHOTOGRA PHIC PROPERTIES Gamma (contrast) 0.78

Speed 20 Maximum optical density 0.84

Fog level 0.07

EXAMPLE 5 Substantially the same procedure as set forth in Ex ample 1 was followed, but, instead of Cabot P-25, Cabot P- was included as the photosensitive component of the medium. Cabot P-110 is a titanium dioxide produced by the pyrolysis of titanium halides and has an initial average particle size of about 0.1 micron and an initial nitrogen surface area of about 20 square meters per gram.

The photographic properties of the medium were determined and the following data were obtained:

TABLE 5.-PHOTOGRAPHIC PROPERTIES Gamma (contrast) 0.73 Speed 10 Maximum optical density 1.1 Fog level 0.08

EXAMPLE 6 Substantially the same procedure as set forth in Example 2 was followed, but, instead of Cabot P-25, Cabot P-llO was heated in air at a temperature of 500 C. for about 5 hours.

The photographic properties of the image storage medrum comprising the Cabot P-110 so heat treated were determined and the following data were obtained:

TABLE 6.-PHOTOGRAPHIC PROPERTIES Gamma. (contrast) 0.65 Speed 32 Maximum optical density 1.0 Fog level 0.07

EXAMPLE 7 TABLE 7.-PHOTOGRAPHIC PROPERTIES Gamma (contrast) 1.0 Speed 35 Maximum optical density 1.5 Fog level 0.11

EXAMPLE 8 A medium prepared in accordance with the procedure set forth in Example 2 was immersed in a saturated solution of silver nitrate in methanol prior to the exposure thereof.

After drying, the medium was exposed to the standard source and developed in accordance with the procedure of Example 7.

The photographic properties of the medium were determined and the following data obtained:

TABLE 8.--PH'OTOGRAPHIC PROPERTIES Gamma (contrast) 1.0 Speed 190 Maximum optical density 1.5 Fog level 0.10

Examples 7 and 8 illustrate the improvements realized when media comprising other photosensitive components include the heat treated titanium dioxides of the present invention.

Many modifications of the details involved in the above examples offered for the purpose of illustrating my invention may be utilized in the practice thereof Without departing from the spirit and scope of the invention defined in the appended claims.

Having described my invention and methods of practicing same together with preferred embodiments thereof, what I declare as new and desire to secure by US. Letters Patents is as follows:

1. In a data storage medium comprising a support and a radiation sensitive titanium dioxide dispersed in a binder, the improvement wherein the titanium dioxide is a titanium dioxide which is heated in an oxidizing atmosphere at an elevated temperature of at least about 200 C. for a time period of at least about 0.5 hour and which had an initial average particle diameter no greater than about one micron and a nitrogen surface area of less than about 60 square meters per gram prior to this heating, the titanium dioxide which is subjected to this heating being such that the photographic speed of the titanium dioxide will be improved by such heating when subsequently utilized in a photographic process involving exposing a copy medium comprising the titanium dioxide and forming a permanent image by contacting with imageforming materials which undergo an oxidation-reduction type reaction.

2. The medium of claim 1 wherein the titanium dioxide is heated in an oxidizing atmosphere at a temperature of at least about 400 C. for a time period of at least about 0.5 hour.

3. The medium of claim 1 wherein the titanium dioxide is heated at a temperature between about 400 C. to about 650 for from about 2 hours to about 5 hours.

4. The medium of claim 1 wherein the titanium dioxide had an initial average particle size no greater than about 0.2 micron.

5. The medium of claim 1 wherein the titanium dioxide to be heated is produced by the high temperature pyrolysis of titanium halides.

6. The medium of claim 1 wherein the titanium dioxide to be heated is produced by the high temperature pyrolysis of titanium halides and had an initial average particle diameter of about 0.03 micron and an initial nitrogen surface area of about 40 square meters per gram.

7. In the process wherein a data storage medium comprising a support and a photosensitive titanium dioxide dispersed in a binder is exposed to establish an image pattern, the improvement wherein the titanium dioxide is a titanium dioxide which is heated in an oxidizing atmosphere at a temperature of at least about 200 C. for a period of time of at least about 0.5 hour and which titanium dioxide had an initial average particle diameter no greater than about one micron and a nitrogen surface area of less than about 60 square meters per gram prior to this heating, the titanium dioxide which is subjected to this heating being such that the photographic speed of the titanium dioxide will be improved. by such heating when subsequently utilized in a photographic process involving exposing a copy medium comprising the titanium dioxide and forming a permanent image by contacting with imageforming materials which undergo an oxidation-reduction type reaction.

8. The process of claim 7 wherein the titanium dioxide is heated in an oxidizing atmosphere at a temperature of at least about 400 C.

9. The process of claim 8 wherein said titanium dioxide is heated at a temperature between about 400 C. to about 650 C. for from about 2 to about 5 hours.

10. The process of claim 8 wherein said titanium dioxide had an initial average particle size no greater than about 0.2 micron.

11. The process of claim 8 wherein said titanium dioxide to be heated is produced by the high temperature pyrolysis of titanium halides.

12. The process of claim 11 wherein said titanium dioxide is produced by the high temperature pyrolysis of titanium halides and had an initial average particle diameter of about 0.03 micron and an initial nitrogen surface area of about 40 square meters per gram prior to this heating.

13. A process for producing an image comprising the steps of:

(a) exposing imagewise a data storage medium comprising a support and a radiation sensitive titanium dioxide dispersed in a binder, which titanium dioxide is heated in an oxidizing atmosphere at elevated temperatures of at least about 200 C. and for a period of time of at least about 0.5 hour and for a period of time suflicient to increase the photographic speed of the medium and which had an initial particle diameter of no greater than about 0.2 micron and a nitrogen surface area of less than about 60 square meters per gram, the titanium dioxide which is subjected to this heating being such that the photographic speed of the titanium dioxide will be improved by such heating when subsequently utilized in a photographic process involving exposing a copy medium comprising the titanium dioxide and forming a permanent image by contacting with imageforming materials which undergo an oxidationreduction type reaction; and

(b) contacting the medium with image-forming materials which undergo an oxidation-reduction type reaction to form a permanent image thereon.

14. The process of claim 13 wherein the titanium dioxide was heated in an oxidizing atmosphere at a temperature of at least about 400 C.

15. The process of claim 14 wherein the titanium dioxide to be heated was produced by the high temperature pyrolysis of titanium halides.

16. The process of claim 14 wherein the titanium dioxide which was heated to increase the photographic speed of the data storage medium is used in combination with at least one other photosensitive material.

17. The proces of claim 14 wherein the data storage medium includes image-forming materials at the time of exposure thereof.

18. In a data storage medium comprising a radiation sensitive titanium dioxide dispersed in a binder, imageforming materials which undergo an oxidation-reduction type reaction, and a support therefor, the improvement wherein the titanium dioxide is a titanium dioxide which had an initial average particle diameter no greater than about one micron and a nitrogen surface area of less than about 60 square meters per gram and which was heated in an oxidizing atmosphere at an elevated temperature of at least about 200 C. and for a time period of at least about 0.5 hour and suflicient to increase the photographic speed thereof, the titanium dioxide Which is subjected to this heating being such that the photographic speed of the titanium dioxide will be improved by such heating when subsequently utilized in a photographic process involving exposing a copy medium comprising the titanium dioxide and forming a permanent image by contacting with image-forming materials which undergo an oxidation-reduction type reaction.

19. A medium as in claim 18 wherein the image forming materials comprise a source of metal ions.

20. A medium as in claim 18 wherein the image forming materials comprise a source of silver ions.

References Cited UNITED STATES PATENTS 3,198,632 8/1965 Kimble et a1. 96-1.8 3,311,452 3/1967 Goodgame et a1 23202 3,317,321 5/ 1967 Chopoorian 96--88 3,380,823 4/1968 Gold 96-27 3,397,982 8/1968 Lane 96-1.5 3,409,429 '11/ 1968 Ekman et a1. 9627 3,424,582 1/ 1969 Berman et a1. 96-48 CHARLES E. VAN HORN, Primary Examiner US. Cl. X.R.

96-1.5, 48 PD, 67, 88; 117--1.7; 106-300; 23-202 R; 252501 

